Template creation using context

[mgodwan]

Description

• Adds logic to create index template through the context field
• Adds validation to not allow using system templates in composed_of
• Adds validation to ensure only pre-determined loaders can add system templates
• Updates logic where template data is applied during index creation/simulation.

Status 7/18: Modify and add new tests for the feature.

Related Issues

Resolves #12683

Check List

• Functionality includes testing.
• API changes companion pull request created, if applicable.
• Public documentation issue/PR created, if applicable.

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[github-actions]

❌ Gradle check result for 8036645: FAILURE

Please examine the workflow log, locate, and copy-paste the failure(s) below, then iterate to green. Is the failure a flaky test unrelated to your change?

[github-actions]

❌ Gradle check result for 7233318: FAILURE

Please examine the workflow log, locate, and copy-paste the failure(s) below, then iterate to green. Is the failure a flaky test unrelated to your change?

[opensearch-trigger-bot]

The backport to 2.16 failed:

The process '/usr/bin/git' failed with exit code 128

To backport manually, run these commands in your terminal:

# Navigate to the root of your repository
cd $(git rev-parse --show-toplevel)
# Fetch latest updates from GitHub
git fetch
# Create a new working tree
git worktree add ../.worktrees/OpenSearch/backport-2.16 2.16
# Navigate to the new working tree
pushd ../.worktrees/OpenSearch/backport-2.16
# Create a new branch
git switch --create backport/backport-14811-to-2.16
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 c76bfebd49c8129b564edc68ce59f01853dc6722
# Push it to GitHub
git push --set-upstream origin backport/backport-14811-to-2.16
# Go back to the original working tree
popd
# Delete the working tree
git worktree remove ../.worktrees/OpenSearch/backport-2.16

Then, create a pull request where the base branch is 2.16 and the compare/head branch is backport/backport-14811-to-2.16.

[shwetathareja]

@dblock we have added one new request body parameter in the template API. Can you please help with details on changes to be made OpenAPI spec as well. cc: @mgodwan

[dblock]

@mgodwan Please open a PR that exercises these changes in that repo, see https://github.com/opensearch-project/opensearch-api-specification/blob/main/DEVELOPER_GUIDE.md for details.